Each of WO2007/110938 and WO2009/110461 (hereinafter referred to respectively as Patent Documents 1 and 2) discloses a vehicle bumper structure which includes a hollow bumper reinforcement and a pair of right and left bumper stays supporting the hollow bumper reinforcement. This bumper structure: absorbs collision energy during a process in which the bumper reinforcement undergoes bending deformation (hereinafter referred to as a “beam deflection process”); absorbs collision energy during a process in which the bumper stays break into the bumper reinforcement (hereinafter referred to as a “beam crushing process; and absorbs collision energy during a process in which the bumper stays are crushed (hereinafter referred to as a “stay crushing process”). Such a bumper structure can increase the amount of collision energy absorbed while lowering the peak of the collision reaction force, and as a result, can reduce a damage to the vehicle body, while preventing malfunctions of safety apparatus (such as, for example, an air-bag) on a light collision. In addition, in a beam deflection process of a bumper reinforcement having a bent portion or a curved portion, collision energy is absorbed during a process in which the bent portion or the curved portion is rectilinearly extended.
The bumper reinforcement of each of Patent Documents 1, 2 includes: a rectangular outer shell; and a partition that partitions the inner space formed within the outer shell into an upper space and a lower space. The partition is provided parallel to the upper wall and the lower wall of the outer shell in a manner to join the front wall with the rear wall. The provision of the partition increases the section stiffness of the bumper reinforcement. Accordingly, it is possible to reduce the wall thickness and thus the weight of the bumper reinforcement without reducing the amount of collision energy absorbed.